Comet nuclei are the frozen reservoirs of dust and ices from
the early solar nebula. In particular, the silicate
mineralogy extant in the early solar nebula are recorded in
the dust properties of comets. Of all solar system bodies,
long period (LP) comets suffered the least post-formation
alteration, thus variations in their grain properties probe
the range of processes contributing to the dust reservoir in
the early solar nebula. The composition of LP comet nuclei
are probed through observations of the coma species.

We present mid-IR observations of two LP comets: C/2001 Q4
(Neat) and C/2002 T7 (Linear). For both comets, we obtained
7.8 -- 13.5~\micron\ spectrophotometric observations using
the NASA IRTF (+MIRSI) on 2005 June 4 -- 2005 June 6 UT.
During the time of the observations, Q4 was at a
heliocentric distance of about 1~AU and T7 was at a distance
of 1.1~AU. Q4 shows a silicate resonance feature due to
small silicate dust grains, similar to earlier observations
on 2005 May 11 UT (Wooden et al.\ 2004, ApJ, 612, L77). T7
shows a very weak silicate resonance feature implying that
the thermal emission from the dust in the coma of T7 was
dominated by grains larger than those in Q4. We also
obtained high spatial resolution 10 and 20~\micron\ images
of T7 using Gemini-S (+T-ReCS) on 2004 July 20 UT to map
the distribution of dust grains in the coma. We will present
our preliminary modeling results of the dust grains in
comets Q4 and T7.